Error : “The process cannot access the file '' because it is being used by another process” while writing the log information

public static void WriteLogFile(string message)
       {
           Console.WriteLine(message);

           if (File.Exists("C:\\log.txt"))
           {
               using (StreamWriter SWriter = File.AppendText("C:\\log.txt"))
               {
                   SWriter.WriteLine(message);
               }
           }
           else
           {
               using (StreamWriter SWriter = File.CreateText("C:\\log.txt"))
               {

                   SWriter.WriteLine(message);
               }
           }
       }